Al2O3 films on oxidized Si substrates were implanted with 800 keV Er ions to peak concentrations ranging from 0.01 to 1 at. %. The samples show relatively broad photoluminescence spectra centered at λ=1.533 μm, corresponding to intra‐4f transitions in Er3+. At an Er peak concentration of 0.23 at. %, post‐implantation thermal annealing up to 950 °C increases the photoluminescence intensity by a factor 40. This is a result of defect annealing, which increases the luminescence lifetime from 1 to 7 ms, as well as an increase in the Er3+ active fraction. High Er concentrations are achieved with only moderate concentration quenching effects.

Described here is the first known demonstration of a registered two level guided wavepolymeric electro‐optic Mach–Zehnder intensity modulator array. The device consists of two complete vertically stacked levels. Both levels were independently poled and operated. There was no measurable optical or electrical cross talk due to a high resistivitythermoset polymerbuffers layer employed. Fabrication and performance of the device is discussed.

Nonlinear optical films of LiTaO3 were epitaxially grown on (NH4)2Sx‐treated (111) GaAs using e‐beam evaporated MgO as intermediate layers. The MgO lattice was found to rotate by 180° about the [111] surface normal with respect to the GaAs substrate. The laser‐ablated LiTaO3film grew epitaxially in the preferred [0001] direction and formed a waveguide with its underlying buffer layer of MgO.

Reflectance modulation measurements on red‐emitting GaInP quantum well ridge lasers show a sensitive dependence of the laser mirror temperatures on the number of quantum wells, the type of cladding layers, the configuration of a heat spreader layer covering the ridge waveguide, and on how the laser is mounted on a heat sink. The temperature versus injection current curves also demonstrate the contribution of laser radiation heating even in single quantum well lasers. The temperatures decay rapidly from the mirror into the cavity within about 6 μm (1/e‐point) as found from spatially resolved electroluminescence spectra detected along the laser cavity.

Light‐controlled deposition of potassium atoms onto a glass surface by light‐induced drift (LID) is demonstrated. The collection of atoms by wave‐front curvature is found to be important for maximizing the deposition rate. The light control of diffusive deposition is demonstrated by using LID to push atoms away from surface regions where a layer is not wanted. The measured spatial resolution of this process in the experiment was about 100 μm. Pressure and intensity effects on both deposition processes are discussed.

Single‐crystalline vanadyl phthalocyanine film has been grown by the molecular‐beam epitaxy technique. The χ(3) components, χ111 and χ1111, have been determined by third‐harmonic generation using a fundamental Nd:YAG laser source. The relation, χ1221∼0.8χ1111, reveals that the nondiagonal component significantly contributes to the nonlinear optical response, which originates in two‐dimensional π‐electron system of this molecule.

We investigate the polarization properties of a vertical cavity surface emitting laser that uses an (Al0.5Ga0.5As)1/2(GaAs)1/2 fractional‐layer superlattice (FLS) as an anisotropic gain medium. The anisotropy in the gain enables us to both control and switch the polarization state of the optically pumped lasing output. We obtain room‐temperature lasing for wavelengths from 690 to 720 nm. The output is linearly polarized and the polarization direction is fixed, either parallel or perpendicular to the FLS layers. By tuning the cavity resonance wavelength, we demonstrate high contrast switching between two orthogonal linear polarization states in the FLS surface emitting laser.

We systematically studied microcavity enhancement and mode‐coupling effects in photo‐ and electroluminescence of an AlGaAs/GaAs vertical‐cavity light‐emitting diode(LED) by continuously changing the microcavity resonance with respect to the quantum wellband gap. At mode overlap we obtained maximum photo‐ and electroluminescence intensities and a minimum emitted linewidth of 4.6 nm at 836 nm with a FWHM divergence of 62°. However, the electrical‐to‐optical efficiency was less than 1 μW/mA. Application issues for optical interconnects are presented.

We report on the effect of carrier escape time on the performance of semi‐insulating photorefractive self‐electro‐optic effect devices by investigating three samples of Cr‐doped GaAs/AlxGa1−xAs multiple quantum wells of varying barrier thickness and height. Reduction of barrier thickness from 100 to 35 Å and Al fraction from 0.42 to 0.29 results in a three orders of magnitude increase in diffraction efficiency at a given voltage. The effect of shorter carrier escape and sweep‐out times on the diffraction efficiency, resolution, and sensitivity of these devices is discussed.

Ceramic bearing balls are desirable for use in high‐temperature and nonlubricative environments because of their ability to retain high mechanical strength and reduced wear. However, because ceramics are brittle, it is very important to inspect ceramic parts for the existence of small (1–10 μm) surface defects. The contact–contact resonant sphere technique has been shown to be able to detect the presence of surface defects in spherical objects. This technique, however, has certain limitations that are especially important when inspecting small spheres. In this letter we present a true one‐point‐contact technique to circumvent these limitations. We excite resonances of spheres at both low and high frequencies. Resonances are generated by forming a one‐point Hertzian contact between the sphere and a spherical depression in a buffer rod with a transducer. The resonance spectrum is detected from the opposite pole of excitation using an optical interferometer. At low frequencies, bulk resonances of the sphere are excited, and material properties are determined. At high frequencies, surface‐wave resonances of the sphere are excited, and the dispersion relation of the waves is measured. The measureddispersion relation of the sphere is correlated to the surface wave velocity on the sphere and to the presence of surface defects.

Preferential sputtering has been one of the major problems in sputter depth profiling. Especially for compounds, preferential sputtering of one component leads to a change in the chemical state of the sample constituents. Therefore, accurate sputter depth profiling of the undistorted chemical state of sample constituents has not been possible. In this letter, we report that the preferential sputtering of oxygen atoms in the depth profiling of a Ta2O5 thin film on Si could be reduced quite successfully by using energetic oxygen ion beams with an appropriate incidence angle (30°) from the surface normal. By choosing an appropriate ion incidence angle, oxidation of the metallic Ta by the incident oxygen ion beams could be avoided as well. It was therefore possible to obtain an essentially undistorted sputter depth profile of the Ta in Ta2O5 on Si.

Siliconcarbide(SiC)thin films were deposited on titaniumcarbide (TiC) substrates by pyrolysis of 1,3 disilacyclobutane (C2H8Si2), at atmospheric pressure, in an inverted‐vertical cold‐wall chemical vapor deposition reactor. The growth rate, morphology, and crystallinity of the films were studied, at constant C2H8Si2 flow rate, as a function of substrate temperature (810 °C≤Ts≤1285 °C). The growth rate increased with increasing Ts. Film morphologies were dependent on Ts and slight differences in TiC substrate orientation at Ts≥1015 °C. A smooth, soft as‐grown morphology was obtained at 810 °C. Hard, rough as‐grown surfaces were obtained at Ts≥1066 °C. Filmsgrown at Ts ≥1066 °C contained a SiC primary phase and a Si‐rich second phase. Epitaxialgrowth of β‐SiC was obtained only at 1210 °C.

Based on an x‐ray photoelectron spectroscopy(XPS)analysis, we could gain new implication on the growth mechanism of hydrogenated amorphous silicon (a‐Si:H) from SiH3 radicals. Despite the choice of a considerably small deposition rate and a chemically inert graphite substrate, the substrate signal underwent approximately single‐exponential decay with deposition time. Within the capability of XPS of distinguishing different film‐growth modes, as independently tested by comparing XPS and scanning tunneling microscopy data taken for sputter‐deposited gold, the occurrence of a layerlike a‐Si:H growth is strongly suggested.

We directly observe by reflection high‐energy electron diffraction, the quasiepitaxial growth of crystalline organic quantum‐well structuresgrown by the ultrahigh vacuum process of organic molecular beamdeposition. We show that each of four alternating layers of two organic molecules grows in a crystalline form without sufficient strain to induce amorphous growth, regardless of significant lattice mismatch which might exist between the alternating films. Our results clearly demonstrate the ability to engineer a completely new class of van der Waals‐bonded thin film materials and structures based on crystalline organic semiconductors, with applications to optoelectronics.

A method has been demonstrated to directly observe the surfacecrystallography and defectstructures in diamondfilms by scanning electron microscopy. Individual diamond crystals in the polycrystalline films are polished to a rms smoothness of less than 2 nm using iron metal at temperatures in excess of 725 °C. In the absence of topography, the detailed microstructure of the films can be characterized by secondary electron imaging in a scanning electron microscope by charge‐induced electron contrast which shows strong beam voltage dependence. It is hypothesized that defects and grain boundaries form a connected pathway in the film which has greater conductivity than the generally insulating diamond and creates the charge‐induced contrast.

The temperature dependence of the growth kinetics on V‐grooved substrates is studied by computer simulation, with attention focused upon the evolution of the morphology. We find a distribution of growth rates on GaAs(001) at high temperatures due to surfacediffusion of adatoms from one facet to the other. However, at low temperatures, where surface migration processes are less important, growth on these substrates proceeds in a shape‐preserving manner. Comparison with scanning microprobe reflection high‐energy electron‐diffraction intensity oscillations on GaAs(001) near (111) surfaces shows that our results are in qualitative agreement with observed behavior.

A new noncontact calorimetric method has been developed based on inductive heating of a metallic spherical bulk sample by a power‐modulated radio‐frequency field under ultrahigh vacuum conditions. From the pyrometrically measuredtemperature response the specimen’s external (due to radiative heat loss) and internal relaxation time (due to thermal conductivity) are found to differ by more than two orders of magnitude allowing the specific heat as well as thermal conductivity of the sample to be determined as a function of temperature. The agreement between the measured and predicted temperature response for solid Nb demonstrates the applicability and accuracy of the method which is particularly useful for metastable or chemically reactive samples at high temperature.

Raman spectra of diamondpowders with size less than 2 μm have been measured as a function of the particle size. The Raman line was found to become more asymmetric with some tailing towards lower Raman shifts, broader, and weaker with decreasing particle size. The observed result can be explained by a phonon confinement effect rather than by a strain effect. This work predicts that it is very difficult to detect Raman spectra of diamond particles with size less than ∼50 Å. A broad Raman band, whose intensity becomes stronger with decreasing particle size, was observed around 600 cm−1 in the spectra of diamondpowders with particle size less than 2 μm. We hypothesize that the broad band arises from transverse acoustic phonons near the Brillouin zone boundary because of the relaxation in the wave vector selection rule.

Shrinkage of ultralarge scale integrated circuit design rules to below 0.5 μm is placing new demands upon thin‐film interconnect, especially for filling vias in insulating material to conductors lying below. Selective area deposition which will lead to enhanced via filling is investigated here using cluster beams, with a distribution peaking at 2200 atoms in average size, in which every cluster is positively ionized. A positive repelling voltage is placed on a conducting plate immediately behind test substrates which consist of an insulator with overlying conductive test patterns held at ground. Depositing metal selectively coated the conductive patterns while the repelling voltage essentially eliminated deposition onto insulating areas.

We report the fabrication and characterization of a high‐quality two‐dimensional electron system in the X‐point valley of an AlAs quantum well. The modulation doped structure has a density of ns=2.5×1011 cm−2 and low‐temperature mobility μ=3×104 cm2/V s. Cyclotron resonance data reveal an effective massmc=0.46m0, indicating that the X‐point conduction valleys with heavy in‐plane mass are occupied. In the magnetotransport data, we observe quantum Hall states at consecutive integral Landau‐level fillings (ν), implying that the degeneracy of these valleys is lifted. Our data at high magnetic fields show well‐developed fractional quantum Hall states at ν=1/3 and 2/3 with a gap of 1/3Δ=1.3K for the ν=1/3 state at B≊30 T.